Failure of Cement-Augmented Pedicle Screws in the Osteoporotic Spine

摘要

The treatment of patients with osteoporosis and spinal abnormalities that require surgical intervention is difficult because of the challenge of achieving fixation in osteoporotic bone. As the population ages, this challenge is becoming a common problem in the field of spinal surgery. Although numerous publications exist about the biomechanical benefits of various fixation devices and techniques, no standard of care has emerged that offers a clear method for accomplishing spinal stabilization in such patients. This case presents the failure mode of cement-augmented pedicle screws in a patient with severe osteoporosis, a description of the methods used to attain fixation and spinal stability during the revision surgery, and the outcome achieved for the patient 1 year after surgery. An 82-year-old female with a T9 burst fracture and a history of osteoporosis underwent minimally invasive instrumentation from T5 to T12, fusion from T7 to T11, and decompression from T8 to T10. Four weeks after surgery, the patient returned to the hospital because of back pain. Imaging studies showed that the pedicle screws at T11 and T12, which were augmented with polymethylmethacrylate (PMMA), had pulled out of the vertebral bodies. The pedicle screws failed by disengaging from the PMMA and displacing posteriorly and inferiorly. The PMMA did not appear to move during this process. A revision surgery was performed, in which the posterior construct was extended caudally and cephalad, the pedicle screws were augmented with PMMA, and a titanium hook and woven polyester band were used to increase the points of fixation. At 1-year follow-up after revision, our patient showed radiographic evidence of fusion, and the construct continued to maintain stability in the osteoporotic spine.